WO2024042761A1

WO2024042761A1 - Space floating video display device

Info

Publication number: WO2024042761A1
Application number: PCT/JP2023/012608
Authority: WO
Inventors: 宏明 ▲高▼橋; 浩二平田; 浩司藤田
Original assignee: マクセル株式会社
Priority date: 2022-08-23
Filing date: 2023-03-28
Publication date: 2024-02-29
Also published as: JP2024029819A

Abstract

Provided is technology that is suited for use in a room interior and with which it is possible to display a space floating video with high visibility. The present invention contributes to the Sustainable Development Goals of "3. Health and well-being for all" and "9. Build a foundation for industry and technological innovation." This space floating video display device comprises a casing 106 in which a video display device 1 is stored, and which can be suitably mounted on the surface of a table, for example, in a room interior. A retroreflective member 2 provided with a λ/4 plate 21 and a polarization separation member 101 (beam splitter) disposed at a predetermined angle are provided outside the the casing 106. Video light of P-polarized light from the video display device 1 is converted into S-polarized light through the polarization separation member 101, the retroreflective member 2, and the like, and a space floating video 3 is displayed at a prescribed location on the basis of video light of the S-polarized light.

Description

Space floating video display device

The present disclosure relates to technology for a spatially floating video display device.

An example of a spatially floating video display device is JP-A-2019-128722 (Patent Document 1). Patent Document 1 states, ``The CPU of the information processing device includes an approach direction detection section that detects the direction in which the user approaches an image formed in the air, and an input coordinate detection section that detects the coordinates at which the input is detected. , includes an operation reception unit that processes the reception of an operation, and an operation screen update unit that updates the operation screen according to the received operation.When the user approaches the image from a predetermined direction, the CPU detects the movement of the user. is accepted as an operation, and the process corresponding to the operation is executed.''

JP2019-128722A

Although the spatially floating video display device as disclosed in Patent Document 1 can improve the operability of the spatially floating video, it does not take into consideration the improvement in the apparent resolution and contrast of the spatially floating video. There is a real need for further improvement in the quality of floating images.

Floating video display devices have a wide range of uses, and when used as signage (advertisement billboards), they attract the attention of many people due to the unusual feature of ``images floating in space,'' which is not found on conventional flat displays. Effects can be obtained. Furthermore, as described in Patent Document 1, if a floating image is used as a human interface for performing some kind of operation, the non-contact feature prevents virus infection through contact parts such as push buttons. Effects can be obtained. Furthermore, if a floating image display device could be easily installed in a home's study, living room, or workplace, characters, figures, or videos that were previously simply displayed on an LCD screen could be displayed as floating images. It is visually pleasing and suitable as an interior accessory.

On the other hand, when using a spatially floating video display device indoors, especially in a living room where families gather or an office where at least several people are present at work, the spatially floating video is It is desirable that only the However, as will be described later, there is a problem in that the image light emitted from the image source that is the source of the spatially floating image can be seen even by a person on the opposite side of the user's eye position. It has been desired to solve this problem, that is, to make the image light invisible to people other than the user who are on the opposite side of the user's eye position.

An object of the present disclosure is to make it possible to prevent the image light from being visible to a person on the opposite side of the user's eye position when the user views the spatially floating image with respect to a spatially floating image display device. The goal is to provide technology. Further, an object of the present disclosure is to provide a technology that is suitable for indoor use and can display a highly visible spatial floating image.

In order to solve the above problem, for example, the configuration described in the claims is adopted. The present application includes a plurality of means for solving the above problems, and one example is as follows. A space-floating video display device according to an embodiment is a space-floating video display device that displays a space-floating video, and is disposed opposite to the video display device, and has a λ/4 plate (retardation plate) on a retroreflective surface. a retroreflective member provided with a quarter-wave plate), and polarized light arranged at a predetermined angle with respect to the video display device and the retroreflective member in a space connecting the video display device and the retroreflective member. The image display device includes a light source device and a liquid crystal display panel as an image source, and the image light of a specific polarization emitted from the liquid crystal display panel, specifically, P The polarized image light passes through the polarization separation member (also referred to as a beam splitter), is reflected by the retroreflection member, and passes through the λ/4 plate twice to be polarized into S-polarized image light. Ru. As a result, the S-polarized image light reflected by the retroreflection member is reflected by the polarization separation member, and a spatial floating image, which is a real image, is displayed at a predetermined position based on the reflected image light.

Here, when the P-polarized image light passes through the beam splitter, a part of the P-polarized image light is reflected without passing through the beam splitter. A portion of the reflected image light reflected by this beam splitter can be seen by a person on the back side of the floating image display device, more specifically, from a person on the opposite side from the eye position of the user viewing the floating image. This problem arises.

The spatially floating image display device of the present embodiment has a configuration in which the reflected image light reflected by the beam splitter is not generated, or the amount of the reflected image light is sufficiently reduced. More specifically, the spatial floating image display device of this embodiment sets the incident angle of the image light (P-polarized image light) to the beam splitter at a predetermined angle (Brewster's angle: θB), so that The structure is such that the reflected image light does not occur.

According to a representative embodiment of the present disclosure, regarding a space floating video display, when a user views a space floating video, video light is visible from a person on the opposite side of the user's eye position. You can make it impossible. Further, according to the representative embodiment, it is possible to display a floating image in space that is suitable for indoor use and has high visibility. According to the representative embodiment, a bright and highly visible spatially floating image can be displayed, and reflected image light that is generated when the image light that forms the spatially floating image is reflected by a beam splitter does not occur. , or a configuration that sufficiently reduces the amount of reflected image light. Thereby, it is possible to provide a spatially floating image display device that provides the effect that the reflected image light cannot be seen by a person on the opposite side of the user's eye position. The above-mentioned problems, problems other than the above, configurations for solving these problems, effects, etc. will be made clear by the description of the embodiments below.

FIG. 1 is a diagram illustrating an example of a usage pattern of a floating image display device according to an embodiment. 1 is a diagram showing a V-shaped configuration as an example of the main part configuration of a floating image display device according to an embodiment; FIG. 1 is a diagram illustrating a Z-shaped configuration as an example of a main configuration of a floating image display device according to an embodiment; FIG. FIG. 3 is a diagram showing an example of a detailed structure of a retroreflective member. FIG. 3 is a characteristic diagram showing the relationship between the surface roughness of a retroreflective member and the amount of blur of a retroreflective image (a spatially floating image). 1 is a diagram illustrating a configuration example of a video display device according to an embodiment. 1 is a diagram illustrating an example of the external configuration of a floating image display device according to an embodiment (first embodiment); FIG. 1 is a diagram illustrating a cross-sectional configuration example of a floating video display device according to an embodiment (first embodiment) when viewed from the side; FIG. FIG. 2 is a perspective view showing an example of the external configuration of a floating image display device according to an example (second example). FIG. 2 is a diagram illustrating a cross-sectional configuration example of a floating image display device according to an embodiment (second embodiment) when viewed from the side. FIG. 3 is a diagram showing the relationship between the incident angle and reflectance, and the Brewster angle. FIG. 2 is a perspective view showing an example of the external configuration of a floating video display device according to an embodiment (third embodiment). FIG. 7 is a diagram illustrating a cross-sectional configuration example of a space floating video display device according to an embodiment (third embodiment) when viewed from the side. FIG. 7 is a diagram illustrating an example of mounting a λ/2 plate in a video display unit in a floating video display device according to an embodiment (a modification of the second embodiment).

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same parts are generally designated by the same reference numerals, and repeated explanations will be omitted. In the drawings, the representation of each component may not represent its actual position, size, shape, range, etc. in order to facilitate understanding of the invention. For the purpose of explanation, when explaining processing by a program, the program, function, processing unit, etc. are sometimes explained as the main body, but the main body of hardware for these is the processor or the controller made up of the processor, etc. , equipment, computers, systems, etc. A computer executes processing according to a program read onto a memory, using resources such as a memory and a communication interface as appropriate by a processor. Thereby, predetermined functions, processing units, etc. are realized. The processor is composed of, for example, a semiconductor device such as a CPU/MPU or a GPU. A processor is composed of devices and circuits that can perform predetermined operations. The processing is not limited to software program processing, but can also be implemented using a dedicated circuit. As the dedicated circuit, FPGA, ASIC, CPLD, etc. can be applied. The program may be installed as data in the target computer in advance, or may be distributed as data from a program source to the target computer and installed. The program source may be a program distribution server on a communication network, or may be a non-transitory computer-readable storage medium such as a memory card or disk. A program may be composed of multiple modules. A computer system may be configured by multiple devices. The computer system may be configured with a client/server system, a cloud computing system, etc. Various types of data and information are configured, for example, in a structure such as a table or a list, but are not limited thereto. Expressions such as identification information, identifier, ID, name, number, etc. can be replaced with each other.

<Embodiment>
The spatially floating image display device according to the embodiment includes an image display device, a beam splitter which is a polarization separation member, and a retroreflection device in which a λ/4 plate (retardation plate, quarter wavelength plate) is provided on a retroreflection surface. and a reflective member. A video display device includes a light source device and a display panel or liquid crystal display panel that emits video light of a specific polarization (for example, P-polarized light) as a video source (video display element). The light source device generates and supplies light as a backlight to the liquid crystal display panel. A polarization separation member is arranged in a space connecting the liquid crystal display panel of the video display device and the retroreflection member. The polarization separation member transmits image light of a specific polarization from the liquid crystal display panel toward the retroreflection member, and converts the image light of the other polarization (for example, S-polarized light) into the other polarization after polarization conversion by the retroreflection member and the λ/4 plate. ) has the property of reflecting image light. After reflection, the image light of the other polarization generates and displays a spatially floating image, which is a real image, at a predetermined position in a direction different from that of the image display device.

The image display device may be provided with a polarization conversion unit that aligns the light source light from the light source device to polarization in a specific direction in order to improve the contrast performance of the spatially floating image. For example, a light source device includes a point-like or planar light source, an optical element section that reduces the divergence angle of light from the light source, and a polarization conversion section (such as a polarization conversion element) that aligns the light from the light source with polarization in a specific direction. and a light guide having a reflective surface that propagates the light from the light source to the liquid crystal display panel, and controls the image luminous flux of the image light from the liquid crystal display panel by the shape and surface roughness of the reflective surface of the light guide. .

The space-floating video display device of the embodiment is designed to be used particularly, but not exclusively, indoors, and includes a video display device portion having a casing that can be installed on a desk, and a space-floating video display portion having a frame structure. It is composed of

The video display device section mainly includes a liquid crystal display panel and a light source (backlight).

The spatially floating image display section is configured with an optical system consisting of a polarization separation member, a retroreflection member, and the like. The optical system of this embodiment has a structure supported by a frame made of metal or resin.

[Spatial floating image display device]
In the following embodiments, for example, an image generated by image light from a large-area image light source is transmitted through a transparent member that partitions the space, such as the glass of a shop window, to create a space inside or outside the store space. The present invention relates to a spatial floating image display device that can display floating images. In addition to the above-mentioned embodiments, an image generated by image light from an image light emitting source having a smaller area (for example, about 2 to 5 inches) can be produced using a polarization separation member (in other words, a polarization beam splitter, or simply a beam The present invention relates to a spatially floating image display device that uses an optical system composed of a splitter (splitter) and a retroreflector, and is mainly used for displaying spatially floating images indoors.

In the following description of the embodiment, an image floating in space is expressed using the term "space floating image." Instead of this term, it may be expressed as "aerial image", "aerial floating image", "aerial floating optical image of a displayed image", "aerial floating optical image of a displayed image", etc. The term "space floating image" used in the description of the embodiments is used as a representative example of these terms.

According to the following embodiments, it is possible to display high-resolution video information floating in space, for example, on the glass surface of a show window or on a light-transmitting board. Further, the spatial floating image display device of the embodiment can be installed in a relatively small space such as on a desk in a study, on a table in a living room, or at a kitchen counter. Further, according to the embodiment, in particular, the reflected image light (details will be described later) is made invisible to the user who can see the spatially floating image, but to the person on the opposite side of the spatially floating image display device. It becomes possible to provide a spatially floating image display device. According to the embodiment, it is possible to provide a spatially floating video display device that is particularly suitable as a display device for interior accessories or information equipment indoors.

The spatially floating image display device of the prior art uses an organic EL panel or a liquid crystal display panel as a high-resolution color display image source in combination with a retroreflective member. In the spatially floating image display device of the prior art example, the image light is diffused over a wide angle, and therefore the following problems occur.

As shown in FIG. 4, in the retroreflective member 2, since the retroreflective portion 2a is a hexahedron, in addition to the normally reflected reflected light, a ghost image is created by the image light incident obliquely on the retroreflective member 2. There was a problem in that the image quality of floating images was degraded. The retroreflective member 2 is also called a retroreflective plate, a retroreflective sheet, or the like.

In addition, as shown in FIG. 5, the spatially floating image obtained by reflecting the image light from the image display device, which is the image source, on the retroreflective member 2 includes the pixels of the liquid crystal display panel, in addition to the above-mentioned ghost image. There was also the issue of blurring occurring at different times.

FIG. 1 shows an example of a usage pattern and a configuration example of a spatially floating video display device according to an embodiment. FIG. 1A shows the overall configuration of a spatially floating video display device according to this embodiment. For example, in a store or the like, a space is partitioned by a show window (window glass) 105 that is a light-transmissive member (also referred to as a transparent member) such as glass. According to the spatial floating information display device of this embodiment, the spatial floating image can be displayed in one direction to the outside of the store space through the transparent member. Specifically, light with a narrow directional characteristic and a specific polarization is emitted from an image display device 1 in a space floating information display device as an image light beam, once enters a retroreflective member 2, and is retroreflected. , a real image floating in space 3 is formed outside the store space through the window glass 105. FIG. 1A shows a case where, in the depth direction, the back side of the window glass 105 is the inside of the store, and the front side is the outside of the store (for example, a sidewalk). On the other hand, by providing a means (such as an optical member) for reflecting specific polarized waves on the window glass 105, it is also possible to reflect the image light flux and form the spatially floating image 3 at a desired position within the store.

FIG. 1B shows a block configuration of the video display device 1 described above. The video display device 1 includes a video display section 1a that displays the original image of the spatial floating video 3, a video control section 1b that converts the input video according to the resolution of the panel of the video display section 1a, and receives a video signal. The video signal receiving unit 1c includes a video signal receiving unit 1c and a receiving antenna 1d. The video signal receiving unit 1c supports wired input signals such as USB (Universal Serial Bus: registered trademark) input and HDMI (High-Definition Multimedia Interface: registered trademark) input, as well as Wi-Fi (Wireless Fidelity: registered (Trademark) and other wireless input signals. The video display device 1 functions independently as a video receiving/displaying device, and can also display video information from an external PC, tablet, smartphone, or the like. Furthermore, the video display device 1 can be provided with capabilities such as calculation processing and video analysis processing by connecting a stick PC or the like.

[Spatial floating video display device V type]
FIG. 2 shows an example of the configuration of the main parts of a floating image display device according to an embodiment. The embodiment shown in FIG. 2 shows a configuration in which an image display device 1 and a retroreflective member (in other words, a retroreflective plate) 2 are arranged in a substantially V shape (hereinafter referred to as a V shape). As shown in FIG. 2, in the V-shaped configuration, a specific polarized light is generated in an oblique direction (direction corresponding to the optical axis A1) with respect to a transparent member 100 such as a flat glass (disposed horizontally in this example). The image display device 1 is provided with an image display device 1 that generates image light. Further, a retroreflective member 2 is provided in another diagonal direction (direction corresponding to the optical axis A2) with respect to the transparent member 100 such as flat glass. The video display device 1 includes a light source device 13, a liquid crystal display panel 11 which is a liquid crystal display element, an absorption type polarizing plate 12, and the like.

In FIG. 2, image light of a specific polarization emitted from the liquid crystal display panel 11 of the image display device 1 travels in the direction of the optical axis A1, and selectively reflects the image light of a specific polarization provided on the transparent member 100. It is reflected by the beam splitter 101 (polarization separation member) having a film, travels in the direction of the optical axis A2, and enters the retroreflection member 2. In this example, the beam splitter 101 is formed into a sheet shape and is adhered to the lower surface of a transparent member 100 such as flat glass. Alternatively, the beam splitter 101 may be formed by directly depositing an optical thin film on flat glass.

A λ/4 plate 21 is provided on the image light incident surface (in other words, the retroreflective surface) of the retroreflective member 2. In other words, the λ/4 plate 21 is a polarization conversion element, a retardation plate, and a quarter wavelength plate.

The image light on the optical axis A2 from the beam splitter 101 is passed through the λ/4 plate 21 twice, once when it enters the retroreflector 2 and when it exits from the retroreflector 2. Polarization conversion is performed from a specific polarization (one polarization) to the other polarization. Here, the beam splitter 101 that selectively reflects the image light of a specific polarization has a property of transmitting the image light of the other polarization after polarization conversion. Therefore, the image light of the other polarization after polarization conversion is transmitted through the beam splitter 101. The image light transmitted through the beam splitter 101 forms and displays a spatially floating image 3, which is a real image, at a predetermined position outside the transparent member 100 in the direction of the optical axis A3 corresponding to the optical axis A2.

Note that the light forming the space floating image 3 is a collection of light rays that converge from the retroreflective member 2 to the optical image of the space floating image 3, and these light rays continue to travel straight even after passing through the optical image of the space floating image 3. do. Therefore, in the configuration of FIG. 2, when the user views the image from the direction A indicated by the arrow corresponding to the optical axis A3, the spatially floating image 3 is viewed as a bright image. However, when viewed by another person from the direction B indicated by the arrow, for example, the floating image 3 cannot be viewed as an image at all. Such characteristics are very suitable for use in systems that display videos that require high security or highly confidential videos that should be kept secret from the person directly facing the user.

Note that depending on the performance of the retroreflective member 2, the polarization axes of the reflected image light may become uneven. In this case, some of the image light whose polarization axes are not aligned is reflected by the beam splitter 101 described above and returns to the image display device 1 . When this returned light is reflected again on the image display surface of the liquid crystal display panel 11 that constitutes the image display device 1, a ghost image may be generated and the image quality of the spatially floating image 3 may be degraded. Therefore, in this embodiment, an absorption type polarizing plate 12 is provided on the image display surface of the image display device 1. The image light emitted from the image display device 1 is transmitted through the absorption type polarizing plate 12, and the reflected light returning from the beam splitter 101 is absorbed by the absorption type polarizing plate 12. Thereby, the above-mentioned re-reflection can be suppressed, and image quality deterioration due to ghost images of the spatially floating image 3 can be prevented.

The beam splitter (polarization separation member) 101 described above is formed of, for example, a reflective polarizing plate or a metal multilayer film that reflects a specific polarized wave. More specifically, the beam splitter 101 can be constructed by depositing an optical thin film on flat glass (for example, quartz glass).

[Spatial floating video display device Z type]
FIG. 3 shows a configuration example of a main part of a floating image display device according to an embodiment, which is different from the embodiment shown in FIG. In the embodiment shown in FIG. 3, a video display device 1 and a retroreflective member 2 (retroreflective plate) are arranged facing each other, and a beam splitter 101 is installed between the video display device 1 and the retroreflective member 2 in a space connecting them. This figure shows a configuration (hereinafter referred to as Z-shape) in which they are arranged approximately in a Z-shape (or inverted Z-shape) at an angle of about 45 degrees with respect to each other.

In the Z-type configuration shown in FIG. 3, a transparent member 100 such as a glass plate and a An absorption type polarizing plate 112 is provided. As shown in FIG. 3, the video display device 1 and the retroreflective member 2 are arranged at an angle of approximately 90 degrees with the transparent member 100 and the absorption polarizing plate 112, and are arranged at an angle of approximately 45 degrees with the beam splitter 101. are arranged at an angle. In this embodiment, the beam splitter 101 is arranged in the horizontal direction, and the position of the image displayed on the image display device 1, more specifically, the liquid crystal display panel 11, and the position where the spatial floating image 3 is formed. This means that the beam splitter 101 has a plane-symmetrical positional relationship.

[Retroreflective member]
FIG. 4A shows the surface shape of a retroreflective member 2 (retroreflector plate) manufactured by Nippon Carbide Industries Co., Ltd. used in this study as a typical retroreflective member 2. FIG. 4A shows a top view, and FIG. 4B shows a side view. On the surface of the retroreflective member 2, there is a retroreflective portion 2a formed of regularly arranged hexagonal columns. The light beam that has entered the interior of the retroreflector 2a is reflected by the wall and bottom surfaces of the hexagonal prism, and is emitted as retroreflected light in a direction corresponding to the incident light. This emitted light forms a spatially floating image 3 as a regular reflected image (regular image), for example, in the configuration shown in FIGS. 2 and 3. On the other hand, as shown in FIG. 4B, some of the image light from the image display device 1 that is obliquely incident on the retroreflective member 2 may be placed at a position different from the normal image. A ghost image is formed. This ghost image reduces the visibility of the spatially floating image 3.

Therefore, in this embodiment (FIG. 3), based on the image displayed on the image display device 1, a real image floating in space 3 is displayed without forming a ghost image. The resolution of this spatially floating image 3 largely depends on the outer diameter D and pitch P of the retroreflective portion 2a of the retroreflective member 2 shown in FIG. 4A, in addition to the resolution of the liquid crystal display panel 11. For example, when using a 7-inch WUXGA (1920 x 1200 pixels) liquid crystal display panel 11, even if one pixel (one triplet) is approximately 80 μm, the diameter D of the retroreflective portion 2a is 240 μm and the pitch P is 300 μm, one pixel of the spatial floating image 3 is equivalent to 300 μm. Therefore, the effective resolution of the spatial floating image 3 is reduced to about 1/3. Therefore, in order to make the resolution of the floating image 3 equivalent to that of the image display device 1, it is desirable to make the diameter D and pitch P of the retroreflective portion 2a close to one pixel of the liquid crystal display panel. On the other hand, in order to suppress the occurrence of moiré due to the pixels of the retroreflective member 2 and the liquid crystal display panel 11, it is preferable to design the pitch ratio of each of them to be outside an integral multiple of one pixel. Further, the shape may be such that none of the sides of the retroreflective portion 2a overlaps any one side of one pixel of the liquid crystal display panel 11.

The present inventor has determined the relationship between the amount of image blur l (small L) and the pixel size L (large L) of the image of the spatially floating image 3 that is permissible in order to improve visibility in a liquid crystal display panel 11 with a pixel pitch of 40 μm. The image display device 1 was created in combination with the light source device 13 having a narrow divergence angle (divergence angle of 15°) of this example, and was determined through experiments. FIG. 5 shows the experimental results. It was found that the amount of blur l that deteriorates visibility is desirably 40% or less of the pixel size, and is hardly noticeable if it is 15% or less. The surface roughness of the reflective surface for which this blur amount l is an acceptable level is that the average roughness is 160 nm or less within a measurement distance of 40 μm, and for a less noticeable blur amount l, the surface roughness of the reflective surface is 120 nm or less. was found to be desirable. For this reason, it is desirable to reduce the surface roughness of the retroreflective member 2 described above, and to make the surface roughness including the reflective film forming the reflective surface and its protective film below the above-mentioned value.

On the other hand, in order to manufacture the retroreflective member 2 at a low cost, it is preferable to mold it using a roll press method. Specifically, this is a method in which the retroreflective parts 2a are aligned and shaped on the film. In this method, the reverse shape of the shape to be shaped is formed on the roll surface, an ultraviolet curing resin is applied on the fixing base material, and the resin is passed between the rolls to form the required shape, and is irradiated and cured to obtain a retroreflective member 2 having a desired shape.

The video display device 1 of this embodiment uses a liquid crystal display panel 11 and a light source device 13 (details shown in FIG. 6) as a light source that generates light of a specific polarization to provide an image that is viewed obliquely from the above-mentioned retroreflective member 2. The possibility of image light entering is reduced. As a result, a structurally superior system is obtained in which the generation of ghost images is suppressed, and even if a ghost image occurs, the brightness of the ghost image is low.

On the other hand, in the configuration of the Z-type spatially floating image display device shown in FIG. For example, the beam splitter 101 is arranged at an angle of about 45 degrees with respect to the horizontal beam splitter 101. The image light from the image display device 1 passes through the beam splitter 101 in the direction of the optical axis B1 (diagonal direction with respect to the beam splitter 101), and passes through the beam splitter 101 in the direction of the optical axis B2 (corresponding to the direction D) corresponding to the optical axis B1. Then, it moves toward the retroreflective member 2.

Here, the image light from the image display device 1 is light of a specific polarization, for example, image light having characteristics of P-polarized light (Parallel Polarization). The beam splitter 101 is a polarization separation member such as a reflective polarizing plate, and transmits the P-polarized image light from the image display device 1, but transmits the S-polarized (vertical polarization) image light. It has a reflective property. This beam splitter 101 is formed from a reflective polarizing plate or a metal multilayer film that reflects a specific polarized wave. This beam splitter 101 can generally be formed by depositing an optical thin film on a flat glass substrate. Therefore, the refractive index of the beam splitter 101 has substantially the same value as the refractive index n (n=about 1.5) of the flat glass.

On the other hand, a λ/4 plate 21 is provided on the light incidence surface (retroreflection surface) of the retroreflection member 2. The P-polarized image light transmitted through the beam splitter 101 from the image display device 1 passes through the λ/4 plate 21 twice in total when entering and exiting the retroreflective member 2, thereby converting the P-polarized light into S-polarized light. The polarization is converted to As a result, the S-polarized image light after polarization conversion from the retroreflective member 2 is reflected by the beam splitter 101 and proceeds toward the transparent member 100 and the like. The S-polarized image light that has traveled in the direction corresponding to the optical axis B3 after reflection (oblique direction with respect to the beam splitter 101) is transmitted through the transparent member 100 such as a glass plate and the absorptive polarizing plate 112, and is A spatial floating image 3, which is a real image, is generated and displayed at a predetermined position on the outside.

Here, in order to reduce image quality deterioration due to sunlight and illumination light entering the optical system composed of optical components such as the video display device 1, retroreflective member 2, and beam splitter 101, transparent It is preferable to provide an absorption type polarizing plate 112 on the outer surface of the member 100. Since the polarization axes may become misaligned due to retroreflection of the light by the retroreflection member 2, some of the image light may be reflected by the beam splitter 101 and returned to the image display device 1. This returned light is reflected again on the image display surface of the liquid crystal display panel 11 constituting the image display device 1, thereby generating a ghost image and significantly degrading the image quality of the spatially floating image 3.

Therefore, in both the embodiments shown in FIGS. 2 and 3, an absorption polarizing plate 12 is provided on the image display surface of the image display device 1. Alternatively, an anti-reflection film (not shown) may be provided on the image exit side surface of the absorptive polarizing plate 12 provided on the surface of the image display device 1. As a result, the absorption type polarizing plate 12 absorbs light that causes a ghost image, thereby preventing image quality deterioration of the spatially floating image 3 due to the ghost image.

Furthermore, in the Z-shaped configuration shown in FIG. 3, when external light directly enters the retroreflective member 2, a strong ghost image is generated. Therefore, in order to suppress and prevent the occurrence of this ghost image, in this embodiment, the retroreflective member 2 is tilted downward with respect to the direction of incidence of external light, thereby blocking the incidence of external light. Specifically, the main incident direction of external light is set to be a direction (diagonal direction such as optical axis B3) corresponding to direction C shown by the arrow (direction in which the user views the floating image 3 from the front). . In that case, the retroreflective member 2 is arranged such that the optical axis B2 is at an angle of, for example, about 90 degrees with respect to the direction C (optical axis B3). In other words, the main surface of the retroreflective member 2 is arranged at an angle of, for example, about 90 degrees with respect to the main surface of the transparent member 100 and the like. As a result, external light incident in direction C does not directly enter the main surface (retroreflective surface) of the retroreflective member 2, thereby preventing the generation of ghost images.

Furthermore, the video display device 1 is also arranged in a direction different from the direction of incidence of external light (direction C). Specifically, the main surface (image light exit surface) of the video display device 1 is arranged in the same direction (in other words, parallel) as the main surface of the retroreflective member 2, and the optical axis B1 of the video display device 1 is aligned with the main surface of the retroreflective member 2. It is arranged at about 90 degrees with respect to the optical axis B3 corresponding to the direction of incidence of external light (direction C). Furthermore, when considering the range of luminous flux when external light enters the main surface of the transparent member 100 that functions as an opening in the direction C, the image display device 1 is placed at a position slightly away from the outside of the range. has been done. These reduce the occurrence of ghost images caused by re-reflection on the video display device 1.

[Video display device]
FIG. 6 shows a configuration example of a video display device 1 that is applicable to the embodiments of FIGS. 2 and 3. The video display device 1 includes a light source device 13, a liquid crystal display panel 11, a light direction conversion panel 54, and the like. The aforementioned absorptive polarizing plate 12 may be provided on the image exit surface side of the liquid crystal display panel 11. The light source device 13 includes a plurality of LED elements 201 (LEDs: Light Emitting Diodes) that are semiconductor light sources (solid light sources) constituting a light source, a light guide 203, and the like. FIG. 6 is a developed perspective view showing a state in which the liquid crystal display panel 11 and the light direction conversion panel 54 are arranged on the light output side of the light source device 13.

The light source device 13 is formed of, for example, a case (not shown) made of plastic or the like, and includes an LED element 201 and a light guide 203 housed inside. A light receiving end surface 203a is provided on the light incident side of the light guide 203 in order to convert the diverging light from each LED element 201 into a substantially parallel light beam. The light-receiving end face 203a has a shape in which the cross-sectional area gradually increases toward the side facing the light-receiving part, and has an effect that the divergence angle gradually decreases by being totally reflected multiple times while propagating inside. A lens shape is provided.

Furthermore, a liquid crystal display panel 11 arranged substantially parallel to the light guide 203 is attached to the upper surface of the light guide 203. The upper surface of the light guide 203 refers to an exit surface from which light reflected by the light guide 203 is emitted. Further, a plurality of LED elements 201 are attached to one side surface (lower side surface in FIG. 6) of the case of the light source device 13. The light from the plurality of LED elements 201 is converted into substantially collimated light (substantially parallel light) depending on the shape of the light receiving end surface 203a of the light guide 203. Therefore, the light receiving portion of the light receiving end surface 203a and the LED element 201 are attached while maintaining a predetermined positional relationship.

The light source device 13 is configured by attaching a light source unit in which a plurality of LED elements 201, which are light sources, are arranged on a light receiving end face 203a, which is a light receiving section provided on the light incident side of the light guide 203. The diverging light flux from the LED element 201 is made into approximately collimated light by the lens shape of the light receiving end surface 203a of the light guide 203. This substantially collimated light is guided inside the light guide 203 in the direction A indicated by the arrow. Direction A is a direction substantially parallel to the liquid crystal display panel 11 (from bottom to top in the drawing). The light guided in direction A has its light flux direction converted by a light flux direction conversion unit 204 provided in the light guide 203, and is directed toward the liquid crystal display panel 11, which is substantially parallel to the light guide 203, in the direction B shown by the arrow. emitted to. Direction B is a direction substantially perpendicular to the display surface of the liquid crystal display panel 11.

The light guide 203 has a configuration in which the distribution (in other words, the density) of the light flux direction converting portions 204 is optimized depending on the shape of the inside or surface of the light guide 203. Thereby, the uniformity of the light, which is the light flux emitted from the light source device 13 shown in the direction B and is the light flux incident on the liquid crystal display panel 11, can be controlled.

Furthermore, in the video display device 1 including the light source device 13 and the liquid crystal display panel 11, in order to improve the utilization efficiency of the emitted light flux from the light source device 13 shown in direction B and to significantly reduce power consumption. , the directivity of the light in direction B from the light source device 13 can also be controlled. More specifically, the light source device 13 can be configured as a light source having a narrow divergence angle. As a result, the image light from the image display device 1 efficiently reaches the viewer with high directivity (in other words, straight-line propagation) like laser light, and displays high-quality spatial floating images with high resolution. can. At the same time, the power consumption by the video display device 1 including the LED element 201 of the light source device 13 can be significantly reduced.

In addition, a frame (not shown) of the liquid crystal display panel 11 attached to the top surface of a case (not shown) of the light source device 13 includes the liquid crystal display panel 11 attached to the frame, and a frame (not illustrated) electrically connected to the liquid crystal display panel 11. It is constructed by attaching a flexible printed circuit board (FPC), etc. The liquid crystal display panel 11, which is a liquid crystal display element, generates a display image by modulating the intensity of transmitted light, together with the LED elements 201, based on a control signal from a control circuit (not shown) that constitutes an electronic device.

<Desktop type (Z type) spatial floating video display device>
Next, a desk-mounted space floating video display device according to an embodiment will be described with reference to FIG. 7 and subsequent figures. The basic configuration of the spatial floating video display device of each embodiment shown below corresponds to the Z-type configuration shown in FIG. 3. In order to form the space floating image 3, each component of the space floating image display device (image display device 1, beam splitter 101, retroreflective member 2, etc.) is fixed to each other in a predetermined positional relationship. has been done.

[First example]
FIG. 7 shows an example of the external appearance of a floating image display device suitable for use on a desk, according to an embodiment (referred to as a first embodiment). The space floating video display device of the first embodiment shown in FIG. 7 is roughly divided into a video display device section 300 (corresponding housing 106) and a space floating video display section 400. The video display device section 300 is mounted and housed in the housing 106 (in other words, the storage section of the video display device 1). The floating image display section 400 is composed of a retroreflective member 2, a λ/4 plate 21, a beam splitter 101, a frame 108 that supports them, and the like.

In FIG. 7, when the illustrated XY plane is a desk surface (horizontal surface in this example), the casing 106 is placed on the desk surface. The housing 106 has a generally rectangular shape and a flat plate shape with a predetermined height. The video display device 1 is arranged inside the casing 106 along the desk surface. A floating video display section 400 is arranged above the housing 106. A beam splitter 101 is arranged diagonally with respect to the desk surface. Above the beam splitter 101, a retroreflective member 2 and a λ/4 plate 21 are arranged along the desk surface. The λ/4 plate 21 is arranged facing downward with respect to the retroreflective member 2 located above. That is, the λ/4 plate 21 is arranged on the light incident side of the retroreflective member 2. The spatially floating image 3 is formed between the housing 106 and the retroreflective member 2 so as to come out from the beam splitter 101 to the front side (Y direction) and stand in the vertical direction (XZ plane).

The spatial floating image 3 is formed between the casing 106 and the retroreflective member 2 so as to exit from the beam splitter 101 to the front side (Y direction) and stand in the vertical direction (XZ plane). The housing 106 of the floating image display device is not limited to being placed at the bottom. Depending on the situation, the positional relationship between the housing 106 and the retroreflective member 2 may be reversed, or may be arranged not only vertically but also horizontally. That is, the beam splitter 101 is arranged between the light output side of the housing 106 and the retroreflective member 2, and the light output side of the housing 106 and the light input/output side of the retroreflective member 2 are arranged opposite to each other. The beam splitter 101 is arranged obliquely to the light input/output surface of the retroreflective member 2.

The frame 108 is a member that supports the beam splitter 101, the retroreflective member 2, and the λ/4 plate 21. The frame 108 protrudes upward from the two corners of the top surface of the housing 106, extends diagonally upward along the two oblique sides of the beam splitter 101, bends in the horizontal direction (Y direction), and extends to the retroreflective member 108. , and then their ends extend along the X direction and are closed.

In this embodiment, the components of the video display device 1 as shown in FIG. 6, that is, the light source device 13, the liquid crystal display panel 11, which is a liquid crystal display element, the absorptive polarizing plate 12, etc. are housed and fixed in the housing 106. has been done. An opening 1061 is provided at the top of the housing 106. The opening 1061 is a portion through which image light passes. A transparent member or the like may be provided in the opening 1061. Image light corresponding to an image displayed on the image display device 1, more specifically, on the liquid crystal display panel 11, passes through this opening 1061 and travels toward the beam splitter 101 above.

FIG. 7 shows a perspective view of the external appearance of the floating image display device when viewed from the upper side (diagonally above). Here, the front of the device is a surface corresponding to the direction in which the user can view the space floating image 3 (indicated by a broken line frame) formed by the space floating image display section 400 from the front. Direction F is the direction in which the user views the floating image 3 from the front, and corresponds to the negative direction of the Y direction.

For the purpose of explanation, a coordinate system and directions such as (X, Y, Z) shown in the drawings may be used. The Z direction is the vertical direction, the up and down direction (the vertical direction within the screen of the spatial floating image 3), the X direction and the Y direction are two horizontal directions, and the X direction is the left and right direction (the vertical direction within the screen of the spatial floating image 3). (horizontal direction within the screen), and the Y direction is the depth direction and the front-back direction (the direction in which the user views the spatial floating image 3).

In this embodiment, as shown in the figure, the spatially floating image display section 400 has a configuration in which the beam splitter 101, the retroreflective member 2, etc. are exposed and placed without being covered with a housing. Further, the housing 106 is relatively small (compact) and thin with a small thickness in the Z direction. In this embodiment, the spatial floating image display section 400 is arranged and fixed on the upper side of the housing 106 via a frame 108 which is a support so as to support the beam splitter 101, the retroreflective member 2, etc. . Therefore, when viewing the space-floating video display section 400 (particularly the space-floating video 3) from the user's viewpoint in the Y direction and from the front (direction F), the thin casing 106 is the only casing in the user's field of view. becomes. Therefore, in this embodiment, there are few objects obstructing the user's field of view, and the floating feeling of the floating image 3 can be enhanced, making it suitable for use.

The beam splitter 101 and the retroreflective member 2 are sufficiently thin. The main surface of the retroreflective member 2 made of a resin material is arranged along the X direction and the Y direction (for example, the horizontal direction). Therefore, when the user views the floating image 3 in the Y direction from the front (direction F), the retroreflective member 2 is not very noticeable. Furthermore, when the spatial floating image display unit 400 is not displayed and the spatial floating image display device is not used, and the spatial floating image display unit 400 is viewed from the user's viewpoint in the Y direction (direction F), the beam splitter 101 is It looks like a transparent plate, and the back side of the beam splitter 101 can be seen to some extent.

As already mentioned, the beam splitter 101 has the property of transmitting P-polarized light and reflecting S-polarized light, and can be formed, for example, by depositing an optical thin film on a flat glass substrate. At this time, the incident angle of the polarized light to the beam splitter 101 is generally about 45 degrees ±15 degrees. Further, the video display unit 300, the beam splitter 101, the retroreflective member 2, etc. are arranged and fixed in a predetermined positional relationship, similar to the Z-shaped configuration in FIG.

As shown in FIG. 7, a beam splitter 101 is installed in the XY plane through a frame 108, which is a support, on the housing 106, that is, on the upper side of the image display unit 300 or on the light output side of the image display unit 300. They are arranged so as to form an inclined surface. Further, a retroreflective member 2 and a λ/4 plate 21 are arranged on the XY plane with respect to the beam splitter 101 via a frame 108 that is a support. Here, the beam splitter 101 and the retroreflective member 2 are each fixed at two or three sides of a rectangular main surface by adhering to a frame 108 which is a corresponding support. Then, as shown in the figure, a spatially floating image 3 is formed at a predetermined position in front of the beam splitter 101 in the Y direction.

FIG. 8 shows the internal structure of the video display unit 300 and the floating video display unit 400 of FIG. 7 in a cross-sectional view when viewed from the side and the X direction (direction E in FIG. 7). The video display unit 300 and the floating video display unit 400 have a Z-shaped structure in FIG. 3, as shown. When the configuration of FIG. 3 is rotated in the drawing so that the direction D in FIG. 3 becomes the vertical direction (Z direction), the configuration of FIG. 3 and FIG. has a similar configuration.

In FIG. 8, in the video display device section 300, that is, the housing 106 and the video display device 1 housed in the housing 106, the video light from the liquid crystal display panel 11 is emitted upward in the Z direction. It is located in That is, the image display surface of the liquid crystal display panel 11 is arranged on the XY plane (horizontal plane). Further, within the housing 106, a light source device 13, a liquid crystal display panel 11, and an absorption type polarizing plate 12 are arranged in order from the bottom. In FIG. 8, the image light emitted upward from the image display device 1 onto the optical axis C1 through the opening 1061 is indicated by a broken line arrow. The center of the three broken arrows indicates the optical axis, and the left and right sides indicate the range of the luminous flux.

The image light emitted from the liquid crystal display panel 11 is light having predetermined polarization characteristics, for example, P-polarized light (parallel polarized light: P stands for Parallel). This P-polarized image light passes directly through the beam splitter 101 upward, and travels toward the retroreflective member 2 on the optical axis C2 corresponding to the optical axis C1. The beam splitter 101 has the property of passing P-polarized light and reflecting S-polarized light (vertically polarized light; S stands for Senkrecht). The beam splitter 101 is arranged to form an angle of, for example, about 45 degrees with this P-polarized image light (optical axis C1, Z direction). That is, the beam splitter 101 is arranged so that its main surface forms an angle of about 45 degrees with respect to the Y direction of the main surfaces of the liquid crystal display panel 11 and the retroreflective member 2.

On the other hand, a λ/4 plate 21 is provided on the light incident surface of the retroreflective member 2. The P-polarized image light on the optical axis C2 emitted from the image display device 1 and transmitted through the beam splitter 101 passes through the λ/4 plate twice, once before being reflected by the retroreflective member 2 and once after being reflected. 21, the polarization is converted from P polarized light to S polarized light. As a result, the S-polarized image light that travels on the optical axis C2 after being reflected by the retroreflective member 2 is reflected by the beam splitter 101 and travels on the optical axis C3 in the Y direction. This S-polarized image light generates and displays a spatially floating image 3, which is a real image, at a predetermined position on the near side in the Y direction as shown in the figure.

The predetermined position where the spatially floating image 3 is formed is determined according to the optical distance of the optical path of the optical system including the image display device 1, the beam splitter 101, and the polarization separation member 2. In this embodiment, the space floating image 3 is formed near the front end of the main surface area of the retroreflective member 2 in the depth direction (Y direction). This predetermined position is adjustable by design. As described above, in this embodiment, the spatially floating image 3 is generated by linearly polarized (S-polarized in this embodiment) image light. The user (observer observing the spatially floating image 3) can suitably view the spatially floating image 3 from the front side in the Y direction, that is, from the direction F indicated by the arrow.

In the above embodiment, the image display device 1, the beam splitter 101, and the retroreflective member 2 maintain a Z-shaped positional relationship as shown in FIG. A floating image 3 can be provided. The floating image display device of the above embodiment can be suitably used when placed on a horizontal surface such as a desk, table, or shelf.

Note that when the beam splitter 101 is arranged at an angle of about 45 degrees with respect to the P-polarized image light (optical axis C1, Z direction) as shown in FIG. The image displayed on the liquid crystal display panel 11 is generated and displayed as a spatially floating image 3 while maintaining its aspect ratio. More specifically, when a perfect circle is displayed on the liquid crystal display panel 11, a perfect circle is also displayed as the spatial floating image 3.

[Second example]
Here, when the space floating video display unit 400 of the first embodiment is viewed from the viewpoint of the user (observer) in the Y direction (horizontal direction), that is, as shown in FIG. From direction F, beam splitter 101 looks like a semi-transparent plate. Therefore, while observing the spatial floating image 3, the user can visually recognize the situation on the back side of the beam splitter 101 (the side opposite to the beam splitter 101 when viewed from the user) to some extent. Conversely, this means that the situation on the user's side can also be seen from the back side of the beam splitter 101, that is, from the opposite side of the beam splitter 101 seen from the user, that is, from the direction G in FIG. It means that it is visible to some extent. However, the spatial floating image 3 itself, which is a real image, cannot be viewed from the direction G.

As already mentioned, the beam splitter 101 has the property of transmitting P-polarized light and reflecting S-polarized light, and can be formed, for example, by depositing an optical thin film on a flat glass substrate. Therefore, when the surface of the beam splitter 101 is irradiated with image light (in this case, P-polarized image light emitted from the liquid crystal display panel 11 constituting the image display device 1), most of the light passes through the beam splitter 101. On the other hand, at least a portion of the light irradiated onto the beam splitter 101 is visually recognized as reflected light on the beam splitter 101.

That is, in FIG. 8, when the image light on the optical axis C1 emitted from the image display device 1 is irradiated onto the beam splitter 101, most of the image light (approximately 90% or more) is transmitted to the beam splitter 101. , and reaches the retroreflective sheet 2 , while a portion (approximately 5 to 10%) of the image light is reflected on the beam splitter 101 . This reflected light is shown as reflected image light R.

In other words, in FIG. 8, when the floating image display section 400 is observed from the direction G opposite to the direction F of the original user's viewpoint, the image light reflected on the beam splitter 101 (the reflected image in FIG. There is a problem that light R) can be seen. This reflected image light R is more clearly visible when the brightness around the floating image display section 400 is low, that is, when the room is dark.

Hereinafter, a solution to this problem, that is, a method of making the reflected image light R invisible from the direction G in FIG. 8 or reducing the brightness of the reflected image light R will be described.

9 and 10 show an embodiment in which the space floating video display unit 400 shown in FIGS. 7 and 8 is modified to be more vertically elongated in order to solve the above problem, and the space floating video display device is moved upwardly (diagonally). A perspective view of the exterior as seen from above) is shown. The height of the entire device in the Z direction in FIG. 9 is greater than the height of the entire device in the Z direction in FIG. The angle B2 of the slope arrangement of the beam splitter 101 in FIG. 10 is larger than the angle B1 (approximately 45 degrees) in FIG. 8. As in FIG. 7, the front of the device here is a surface corresponding to the direction F that allows the user to view the space floating image 3 (indicated by a broken line frame) formed by the space floating image display section 400 from approximately the front. In FIG. 9, the Z direction is the vertical direction, the X direction and the Y direction are two horizontal directions, the X direction is the left and right direction (horizontal direction within the screen of the spatial floating image 3), and the Y direction is the depth direction. direction, the front-back direction (the direction in which the user views the spatial floating image 3).

In FIG. 9, similarly to FIG. 7, a beam splitter 101 forms an inclined surface with respect to the XY plane (horizontal plane) on the upper side of the casing 106, that is, the video display unit 300, via the frame 108 that is a support. It is arranged so that Further, a retroreflective member 2 and a λ/4 plate 21 are arranged on the XY plane with respect to the beam splitter 101 via a frame 108 that is a support. Here, the beam splitter 101 and the retroreflective member 2 are each fixed by adhesively bonding two or three sides of a rectangle to a frame 108 which is a corresponding support. As shown in the figure, the space floating image 3 is formed at a predetermined position on the near side in the Y direction with respect to the beam splitter 101 so that the upper part of the space floating image 3 is slightly inclined toward the near side of the user. That is, in the Z direction, the upper part of the spatially floating image 3 is formed to be more inclined toward the user than the lower part of the spatially floating image 3. As illustrated, two sides of the spatial floating image 3 extending in the Z direction are inclined at a predetermined angle γ with respect to the Z direction (vertical direction).

FIG. 10 is a schematic diagram of the floating image display device shown in FIG. 9 viewed from the side, that is, the X-axis direction, direction H in FIG. 9. In addition, in FIG. 10, the above-mentioned direction F is also the negative direction of the Y direction, and direction F' is an oblique direction when the space floating image 3 formed slightly obliquely is viewed from the front (direction perpendicular to the surface). Showing.

In FIG. 10, the image light emitted from the liquid crystal display panel 11 is generally linearly polarized light (S-polarized light or P-polarized light). In the embodiment shown in FIG. 10, the image light emitted from the liquid crystal display panel 11 is P-polarized image light. In this embodiment, in order for the image light to pass through the beam splitter 101, if the image light emitted from the liquid crystal display panel 11 is P-polarized light, it may be emitted as is to the beam splitter 101. On the other hand, when the image light emitted from the liquid crystal display panel 11 is S-polarized light, the S-polarized image light is passed through the λ/2 plate 14 (FIG. 14) in order to convert it into P-polarized light.

FIG. 14 shows an example of the arrangement of the λ/2 plate 14 in an embodiment (a modification of the second embodiment) in which the image light emitted from the liquid crystal display panel 11 is S-polarized light. This λ/2 plate 14 is a separate element from the λ/4 plate 21 of the retroreflection member 2, and is a polarization conversion element, a retardation plate, and a half-wave plate that converts S-polarized light into P-polarized light. . Here, the liquid crystal display panel 11 and the λ/2 plate 14 are arranged, together with the light source device 13 and the absorption type polarizing plate 12, in the housing 106, for example, at the position shown in the figure. In FIG. 14, a λ/2 plate 14 is provided on the image light output surface of the liquid crystal display panel 11 in contact with the upper side in the Z direction, and an absorption type polarizing plate 12 is provided in contact with the upper side of the λ/2 plate 14.

Not limited to the example shown in FIG. 14, as another example configuration, the λ/2 plate 14 may be provided on the lower surface of the transparent member in the opening 1061 of the housing 106.

The P-polarized image light from the liquid crystal display panel 11 in FIG. 10 or the P-polarized image light converted to P-polarized light by the λ/2 plate 14 in FIG. The light passes through the λ/4 plate 21 and enters the retroreflective member 2 . At this time, the image light incident on the retroreflective member 2 passes through the λ/4 plate 21 twice, once upon incidence on the retroreflective member 2 and once upon reflection, so that it is converted into S-polarized image light. The image light reflected by the retroreflective member 2 is converted into S-polarized image light as described above, and is therefore reflected by the beam splitter 101. As a result, a spatial floating image 3 is generated at the position shown in FIG.

At this time, in FIG. 10, the P-polarized image light from the liquid crystal display panel 11 or the image light converted to P-polarized light after passing through the λ/2 plate 14 enters the beam splitter 101. , the ratio of reflection on the beam splitter 101 (reflectance) differs depending on the incident angle α to the beam splitter 101.

The graph shown in Figure 11 represents the incident angle and the reflectance (%R) on the glass surface when S-polarized light and P-polarized light are incident on glass with a refractive index n = 1.5 from the air. It is a graph. In FIG. 11, the curve shown with a broken line shows the change in reflectance with respect to a change in the incident angle of S-polarized image light, and the curve shown with a solid line shows the change in reflectance with respect to a change in the angle of incidence of P-polarized image light. Showing. As shown in FIG. 11, for S-polarized image light, the reflectance increases monotonically as the incident angle increases, whereas for P-polarized image light, the reflectance decreases to 0 as the incident angle increases. , the reflectance becomes 0 at a certain angle, and as the angle of incidence increases, the reflectance increases again. Furthermore, the reflectance of S-polarized image light is always greater than the reflectance of P-polarized image light at the same incident angle.

As shown in FIG. 11, in P-polarized image light, the incident angle at which the reflectance is 0 is called the Brewster angle (denoted as θB). This Brewster angle θB is determined by the following equation 1 from the refractive index of two substances (here, air and glass).

(Formula 1) θB=arctan(n2/n1)

In Equation 1, n1 is the refractive index on the incident side (i.e., air), and n2 is the refractive index on the transmission side (i.e., glass). For example, the Brewster angle θB of light incident on glass having a refractive index of 1.5 from air having a refractive index of 1 is 56.3 degrees.

As is clear from FIG. 11, in the case of S-polarized image light, reflection occurs constantly even if the incident angle is changed, and in the case of P-polarized image light, when the incident angle reaches Brewster's angle θB, the reflection of the material (glass) It goes inside and is no longer reflected. That is, there is a property that the reflectance (%R) becomes 0 at the Brewster angle θB. On the other hand, as is clear from Equation 1, the Brewster angle changes depending on the refractive index of the incident substance, and the larger the refractive index on the transmission side relative to the incident side, the larger the Brewster angle becomes.

As mentioned above, if the configuration is such that P-polarized image light is incident on the beam splitter 101 at the Brewster angle determined by equation 1 from the refractive index (n2) on the transmission side depending on the material of the beam splitter 101, the beam It will no longer be reflected on the splitter 101. As already mentioned, since the beam splitter 101 is formed as an optical thin film on, for example, a plane glass, the Brewster angle θB of the beam splitter 101 is the Brewster angle θB of the glass (more specifically, quartz glass). It has the same value as the angle θB (56.3 degrees).

As a result, in FIG. 10, if the P-polarized image light emitted from the image display device 1 based on the image light from the liquid crystal display panel 11 is incident on the beam splitter 101 at the Brewster angle θB, the beam splitter The reflected image light R reflected on 101 is approximately 0. The reflected image light R cannot be seen from the direction opposite to the direction in which the spatially floating image 3 is formed, specifically, from the direction L in FIG. 10 . This has the effect of making it difficult for others to see the image light, which may be a nuisance to others other than the user of the floating image display device. You can obtain the effect that this will not be seen by others.

Further, as is clear from the graph shown in FIG. 11, the incident angle α of the image light onto the beam splitter 101 is set to the Brewster angle θB (56.3 degrees) or a somewhat smaller angle close to the Brewster angle θB (for example, , an angle within the range from 50 degrees to less than 56.3 degrees) (50 degrees ≦ α < θB), although it is not possible to completely reduce the reflected image light R to 0, the image light beam splitter The reflectance at 101 is 2% or less, and the reflected image light R can be reduced to an almost invisible level. Furthermore, even if the incident angle α to the beam splitter 101 is far from the Brewster angle θB (for example, α<50 degrees), it is clear from the graph shown in FIG. The brightness of the reflected image light R can be reduced simply by converting S-polarized light into P-polarized light using the /2 plate 14.

As described above, the incident angle α at which the image light emitted from the image display device 1 is incident on the beam splitter 101 on the optical axis C1 is set to the Brewster angle θB (specifically, 56.3 degrees) or the Brewster angle θB (specifically, 56.3 degrees). The angle is configured to be within a range close to the star angle θB (50 degrees≦α<θB). That is, as shown in FIG. 10, the angle of arrangement of each component and the like are defined. FIG. 10 is an example in which α=θB. In particular, the angle of the slope of the beam splitter 101 is an angle β (β = 90 degrees - θB = 33.7 degrees) with respect to the Z direction (vertical direction), and an angle β (β = 90 degrees - θB = 33.7 degrees) with respect to the horizontal plane (Y direction). The angle is B2 (B2=θB=56.3 degrees).

As a result, the reflected image light R of the image light at the beam splitter 101 can be reduced to zero or close to zero, to the extent that it does not pose a problem in practice. That is, when the beam splitter 101 is viewed from the opposite side (direction L) from the side where the spatially floating image 3 is visible, the reflected image light R can be reduced to such an extent that it cannot be seen.

The specific incident angle α at the time of incidence on the beam splitter 101 is not limited to the above-mentioned Brewster angle θB, but an effect close to that of the above embodiment can be obtained by setting it to an angle within the range of 45 degrees to 60 degrees. .

[Modified example (third embodiment)]
Here, when the incident angle to the beam splitter 101 is set to Brewster's angle, a new problem as described below arises. As shown in FIG. 8, in the case of a configuration in which the beam splitter 101 is arranged at approximately 45 degrees with respect to the P-polarized image light (optical axis C1, Z direction), That is, the image displayed on the liquid crystal display panel 11 maintains its aspect ratio, and the space floating image 3 is displayed in a direction corresponding to the user's expected line of sight, that is, the horizontal direction (Y direction). Generated and displayed in F.

On the other hand, as shown in FIG. 10, in a configuration in which the incident angle α of the P-polarized image light on the beam splitter 101 is set to 56.3 degrees, which is the Brewster angle θB, the spatial floating image 3 is When viewed from (direction F), it is generated diagonally downward (direction corresponding to direction F'). In FIG. 10, the S-polarized image light from the beam splitter 101 is reflected on an optical axis C3 having an angle corresponding to (θB×2) with respect to the vertical direction (Z direction), as shown. Therefore, the surface of the space floating image 3 has a predetermined angle γ (an angle determined in relation to θB and β) with respect to the XZ plane as a surface perpendicular to the direction of the optical axis C3, and the upper side is the lower side. It is arranged as a slope slanted to the top.

In the case of this configuration, when a user views the floating image 3 in space from direction F, not only does visibility deteriorate, but also a new problem arises in that the floating image 3 cannot be viewed depending on the position of the user's eyes. occurs.

Therefore, FIGS. 12 and 13 show an embodiment that corresponds to a solution to the above-mentioned problem such as deterioration of visibility. FIG. 12 similarly shows a perspective view of the spatial floating image display device of this embodiment. In FIG. 12, the housing 106 has been deformed so that the spatial floating image 3 coincides with the XZ plane. Specifically, the height of the front surface 106s1 of the housing 106 in the Y direction corresponding to the side on which the spatially floating image 3 is formed is made higher than in the case of FIG. 9, and the spatially floating image 3 is formed. The height of the rear surface 106s2 corresponding to the opposite side is lowered. In the example of FIG. 9, the height of the casing 106 in the Z direction is 10 mm, the width in the X direction is 80 mm, and the depth in the Y direction is 30 mm, whereas in FIG. The height is 6 mm. As a result, in FIG. 12, the difference in height between the front side and the back side is 20 mm. On the other hand, the depth between the front side and the back side is the same, 30 mm. Therefore, the floating image display unit 400 in FIG. 12 is tilted backward at an angle arctan(20/30), that is, 33.7 degrees. This 33.7 degrees corresponds to the angle β of the difference between 90 degrees and 56.3 degrees, which is the Brewster angle θB. Alternatively, the angle formed by the light exit surface of the liquid crystal display panel and the light entrance surface of the retroreflective member 2 corresponds to the difference between 90 degrees and the Brewster angle θB.

FIG. 13 shows a cross-sectional view seen from direction H, corresponding to FIG. 12. In FIGS. 12 and 13, the top surface of the housing 106, which has different heights on the front and back sides, is sloped with respect to the XY plane, and the upper side of the top surface has the same positional relationship as in FIGS. A spatial floating image display section 400 is arranged. When the light exit surface of the video display device 1 is disposed along the top surface of the housing 106, the video display device 1 is arranged in a Z-shape with respect to the beam splitter 101 and the retroreflective member 2 within the housing 106. is placed diagonally. That is, the light emitting surface of the image display device 1 or the surface of the liquid crystal display panel is arranged diagonally, or the light emitting surface of the image display device 1 on the side of the casing 106 connected to the beam splitter 101 and the retroreflective member 2 are arranged diagonally. The distance is shorter than the distance between the exit surface of the video display device 1 on the side of the casing 106 that is not connected to the beam splitter 101 and the retroreflective member 2. Alternatively, in the light exit surface of the image display device 1 or the light exit surface of the liquid crystal display panel, the side corresponding to the formed spatially floating image is shorter in distance from the retroreflective member 2 than the side facing the spatially floating image.

Therefore, with the configuration of FIG. 12, the plane on which the spatially floating image 3 is formed coincides with the XZ plane. In the direction of the user's line of sight (direction M corresponding to the negative Y direction in FIG. 12), the spatial floating image 3 has the best visibility from the user's perspective, that is, has high brightness, and The aspect ratio of the spatial floating image 3 also becomes an image having the original aspect ratio (the same aspect ratio as the image displayed on the liquid crystal display panel 11).

As mentioned above, when the incident angle of the P-polarized image light displayed on the liquid crystal display panel 11 to the beam splitter 101 is 56.3 degrees, which is the Brewster angle θB, a spatially floating image as shown in FIG. 3 will be generated diagonally downward, resulting in poor visibility for the user. Therefore, as shown in FIG. 12, by making the front side of the casing 106 containing the image display device 1 higher and the rear side lower, the plane on which the spatially floating image 3 is formed can be made to coincide with the XZ plane. can. This makes it possible to optimize the visibility of the spatially floating image 3, making it suitable for use.

[Effects etc.]
As described above, according to the spatially floating image display device of each embodiment and modification example, it is possible to display a spatially floating image that is suitable mainly for indoor use and has high visibility. Furthermore, the brightness of the reflected image light caused by the image light from the image display device 1 based on the image light from the liquid crystal display panel 11 being reflected on the beam splitter 101 is reduced to zero, or the brightness is reduced. A spatial floating image display device can be provided. As a result, the reflected image light cannot be seen by a person on the opposite side of the spatial floating image display device from a user who is in a position where the spatial floating image can be observed. In a room where a floating image display device is installed, the image light, which is unnecessary or may be bothersome to people other than the user, has the effect of making it difficult to see.

Another reason is that in order to zero or reduce the brightness of the reflected image light, it is necessary to increase the incident angle of the image light to the beam splitter 101 from 45 degrees to 56.3 degrees, which is the Brewster angle θB. Therefore, a problem arises in that the spatially floating image is tilted downward when viewed from the user, resulting in poor visibility. To solve this problem, by appropriately changing the height of the front and rear sides of the casing 106 containing the image display device 1, the surface on which the floating image 3 is formed is set as a vertical plane, and visibility is optimized. It has the effect of being able to

As a result of the above-mentioned effects, the floating image display device of each embodiment and modification example can be used in a relatively small room without emitting unnecessary image light to people other than the user, and is bright and highly visible. It can display an excellent floating image in space, and is small and lightweight, making it suitable for easy installation on a desk, table, or shelf indoors.

With the technology according to this embodiment, by displaying high-resolution and high-brightness video information in a space-floating state, it is also possible to use this space-floating video as a non-contact user interface. , users can operate the device without worrying about contact transmission of infectious diseases. In this way, we will contribute to the 3 Sustainable Development Goals (SDGs) advocated by the United Nations: ``Good health and well-being for all.''

In addition, in the technology according to this embodiment, by reducing the divergence angle of the emitted image light and aligning it with a specific polarization (polarized light), only the regular reflected light is efficiently reflected by the retroreflective member. , which makes it possible to obtain bright and clear spatial floating images with high light utilization efficiency. According to the technology according to the present embodiment, it is possible to provide a contactless user interface with excellent usability and which can significantly reduce power consumption. In this way, we will contribute to the Sustainable Development Goals (SDGs) advocated by the United Nations: ``Create a foundation for nine industries and technological innovation.''

Although the embodiments of the present disclosure have been specifically described above, the embodiments are not limited to the above-described embodiments, and various changes can be made without departing from the gist. Unless specifically limited, each component may be singular or plural. The components of each embodiment can be added, deleted, replaced, etc., except for essential components. A form in which each of the embodiments is combined is also possible.

1: Image display device, 2: Retroreflective member, 3: Space floating image, 11: Liquid crystal display panel, 12, 112: Absorption type polarizing plate, 13: Light source device, 21: λ/4 plate, 100: Transparent member, 101: Beam splitter (polarization separation member), 106: Housing, 108: Frame, 300: Image display unit, 400: Space floating image display unit, 1061: Opening.

Claims

A space floating image display device that displays a space floating image,
A casing housing a video display device;
a retroreflective member disposed outside the casing facing the video display device, and having a λ/4 plate provided on the retroreflective surface;
a polarization separation member disposed at a predetermined angle with respect to the video display device and the retroreflective member in a space connecting the video display device and the retroreflective member outside the casing;
Equipped with
The video display device includes a light source device and a liquid crystal display panel as a video source,
Image light of a specific polarization emitted from the liquid crystal display panel is incident on the polarization separation member at a specific angle of incidence, passes through the polarization separation member, is reflected by the retroreflection member, and is reflected by the λ/ The polarization is converted by passing through the four plates, and the image light becomes the other polarized image, and the other polarized image light is reflected by the polarization separation member, and a predetermined image light is generated based on the reflected image light. Displaying a real image floating in space at a certain location.
Space floating image display device.
The spatial floating image display device according to claim 1,
The image light of a specific polarization that is incident on the polarization separation member is P-polarized light.
Space floating image display device.
The spatial floating image display device according to claim 1,
The specific angle of incidence of the light incident on the polarization separation member is within a range of 45 degrees or more and 60 degrees or less.
Space floating image display device.
The spatial floating image display device according to claim 1,
The specific angle of incidence with respect to the polarization separation member is a Brewster angle corresponding to the material of the polarization separation member, or a range from 50 degrees to less than the Brewster angle, which is smaller than the Brewster angle. is the angle within,
Space floating image display device.
The spatial floating image display device according to claim 4,
The casing in which the image display device is housed has a front surface corresponding to the side on which the space floating image is formed so that the surface on which the space floating image is displayed is a vertical plane. The height is higher than the rear surface,
Space floating image display device.
The spatial floating image display device according to claim 1,
The polarization separation member and the retroreflection member are supported by a frame with respect to the casing in which the video display device is housed.
Space floating image display device.
The spatial floating image display device according to claim 1,
The polarized light separating member includes a reflective polarizing plate or a metal multilayer film that reflects a specific polarized wave, which is formed as an optical thin film on a glass substrate.
Space floating image display device.
The spatial floating image display device according to claim 1,
The surface roughness of the retroreflective surface of the retroreflective member is set so that the ratio of the amount of blur of the spatially floating image to the pixel size of the image display device is 40% or less,
The light source device includes:
A point or planar light source,
an optical element section that reduces the divergence angle of light from the light source;
a polarization conversion unit that aligns the light from the light source with polarization in a specific direction;
a light guide having a reflective surface that propagates light from the light source to the liquid crystal display panel;
Equipped with
controlling the image luminous flux of the image light from the liquid crystal display panel according to the shape and surface roughness of the reflective surface;
Space floating image display device.
The spatial floating image display device according to claim 2,
The image light from the liquid crystal display panel is S-polarized light,
comprising a λ/2 plate that converts S-polarized image light from the liquid crystal display panel into the P-polarized light to be incident on the polarization separation member;
Space floating image display device.